Raw materials for making substrate: straw, hay, husk, bran

Substrates for growing oyster mushrooms are made from various plant materials.

What is the best substrate for growing oyster mushrooms?

The substrate mixture largely depends on the method of heat treatment.

When steaming raw materials in water (hydrothermy), it is not recommended to experiment with multicomponent mixtures.

Each type of vegetable raw material needs a different steaming time. If you are making mixtures, one type of raw material may pick up too much moisture, while another will not have enough time for high-quality heat treatment.

For this reason, the mycelium overgrows with problems.

If you process raw materials by xerothermy (treatment of dry raw materials with steam) or pasteurization in a tunnel, the use of mixtures is welcome.

In this case, in addition to increasing the nutritional value of the composition, its physical structure also improves – this contributes to normal gas exchange in the mushroom block.

The nutritional value of the substrate is determined by the presence of both the main mineral elements and microelements.

In most cases, mushroom growers monitor only the nitrogen content, which should be at least 0.7 – 0.9. Although the successful assimilation of nutrients by the mycelium is also associated with the presence of a certain amount of phosphorus, the ratio of C / N content, and the presence of many trace elements.

Mixtures are made empirically. It is necessary to take into account the amount of nitrogen of each component and the hardness of the plant material.

For example, alfalfa straw is quite tough. It can be combined with soft barley straw. Hay is best used with wheat and rye straw.

The husk can be added to any composition, gradually increasing the percentage of its application and observing overgrowth and yield.

When I say “observing” I mean “recording the results of each batch of blocks.”

The content of the article

So, talking about the most common raw materials for oyster mushroom substrates.

1. Straw of cereals and legumes

Straw is one of the most common ingredients for making oyster mushroom blocks.
It is flattened and crushed with a straw cutter.

Why grind hay and straw?

When crushed, the hollow stem is flattened with a rupture of the internode, since a large number of pathogen spores are located there.
Moreover, straw flattening is much more effective in preventing overgrowth problems than chopping.
Therefore, at large industrial enterprises they do not grind, but already soaked raw materials are crushed by tractors.

Good straw cutters, by the way, not only grind, but, most importantly, cut the stem along. In this case, the internode is torn, and all cavities are well steamed. Any straw fraction is suitable if the stem is flattened. If the straw is only cut, then segments 5-10 cm long are desirable. The straw cutter should grind evenly so that the fine fraction of 1 cm and smaller is no more than 5%.

Hay does not have hollow stalks, but it needs to be crushed to be evenly distributed throughout the mass. After all, there is too much nitrogen in hay, sometimes alfalfa contains up to 3.5-4 units of it according to the Kjeldahl method. Chopped hay is evenly distributed throughout the substrate and the mycelium absorbs nutrients better.

Large lumps of hay in one place do not allow hot water to pass through during hydrothermia and often cause localized rotting, which will eventually spread to the entire bag.
Therefore, hay is not ground separately, but added in small portions when crushing straw bales.

For 100 kg of dry straw take from 5 to 15 kg of hay, depending on its quality.

The difference in the straw of different types of cereals

Stem stiffness

For example, the straw of winter barley is much tougher than that of spring barley.
Triticale has a very hard stem.
When compiling substrate compositions, consider this fact – hard stems absorb water worse.
However, they almost do not crumple, therefore they give the substrate a structural springiness, which makes it possible to achieve the required density.

Nitrogen content (N)

In dry years, it is only 0.2-0.3. For an oyster mushroom, this is very little. Therefore, legume hay must be added to the straw.
Rye straw tends to have a higher N than wheat straw. Although, to a large extent this is due to the conditions for growing cereals.

Availability and price

When you choose which field to harvest straw from, do a nitrogen analysis using the Kjeldahl method in an agrochemical laboratory. It is impossible to do it at home.
It often happens that higher-quality raw materials are not much more expensive, so it is more profitable to buy it.

Soybean and pea straw

The stems that remain after harvesting peas and soybeans can be conventionally called “straw”.

It is used in substrate compositions no more than 20-30%. The percentage of addition is determined by the nitrogen in specific samples and the stiffness of the stems.

I recommend using this straw for xerothermy and pasteurization in tunnels.

Alfalfa straw

How is alfalfa straw different from hay?

Alfalfa straw is obtained when alfalfa is harvested for seed. Hay is harvested when alfalfa is just beginning to bloom.
Straw has many coarse stems and almost no leaves.

The nitrogen content is 1-1.3.

Alfalfa seeds ripen in late summer – early autumn, so when harvesting straw, make sure that there are no hard, thick stems of weeds among it. They reduce the nutritional value of the raw material and can damage the straw cutter.
Also because of this, overgrowing of mycelium can be problematic.

We crushed alfalfa straw separately, for preliminary crushing. From this, the straw cutter knives are very dull, it is necessary to have a spare set of them.

Then the resulting pieces of stems were thrown in small heaps into a straw cutter along with wheat and barley straw.

2. Sunflower husk

The husk has N from 0.6 to 1. A small amount of fragments of sunflower kernels increases the nutritional value of the husk. If there are many kernels, the substrate becomes moldy.

In general, the number of pathogen spores in sunflower husks is much lower than in straw.

Therefore, according to the hydrothermal method, it is kept in hot water for half the time than straw. The processing temperature in both situations is the same.

How to determine the husk is suitable for growing an oyster mushroom block?

Raw material requirements:

Clean and dry (6-10% humidity),
free from dust and pieces of dirt, because they are the sources of pathogens, including rapidly multiplying neurospores.

If the husk is not fresh, stale, it is especially important to check it for moisture and look for mold balls.

When stored in a dry room, where there are few mice, the husk practically does not change its properties – it can be used.
If you go into the warehouse, and there is a smell of dampness or mold, the husk is not crumbly and stinks of mold, it is better not to buy it. With hydrothermia, you will not get rid of the spores that have already formed there in myriad numbers.

Crushed husk

It absorbs too much moisture when steaming, and it is very difficult to reduce it, so it is better not to use such a husk. When adding such husks to straw, take it no more than 20%.

Fat husk

If the husk has a high oil content, you need to monitor the pH. As a result of the saponification reaction of such husks, when lime is added, the pH may rise less than necessary. Therefore, add more lime, controlling the result with a pH meter.
This is why I recommend checking the pH at every sowing, especially if a new batch of husks has arrived.

Does the increased oil content affect the gas exchange in the mushroom block, the overgrowth rate and the yield?

I don’t have hard, verified facts, but logically, this could make it harder for nutrients to dissolve.

In recent years, finding sunflower husks has been problematic in many regions. Fuel briquettes, granules, pellets began to be mass-produced from them.

Pellets can be used as a raw material if no foreign impurities are added to them.

First you need to test on a small batch, if there is a good overgrowth of mycelium, without damage, you can use it.

3. Buckwheat husk

Nitrogen within 0.5-0.7.

Buckwheat husks are used in multicomponent mixtures.

It is impossible to make a substrate only from it. Since, depending on the quality of the husk, the substrate either absorbs too much moisture, or conversely, does not absorb enough water.

If you are experimenting and using only buckwheat husks for the substrate, wait until the mycelium grows in the first batch of mushroom blocks. If the blocks grow well, and the amount of the crop will please you, you can continue.

Please note that the hygroscopicity of buckwheat husks and sunflower husks is very high, it easily absorbs moisture.
At a moisture content above 16%, microbiological activity begins in the raw material, and self-heating in the pile is possible.

Therefore, store the husk in a dry, ventilated room, in polypropylene bags (such as sugar bags) for a short time: a month or two, no longer.

I saw storage in layers at one enterprise: the husk was layered with fine wheat straw. This worked quite effectively – the straw protected the husk from moisture adsorption.

4. Bran for oyster mushrooms

Often on the Internet there is an idea to work with bran, because it has a lot of nutrition for mushrooms.
This idea is bad – bran gives almost 100% damage to the substrate – instead of oyster mushroom mycelium, Trichoderma mold grows in the substrate.

If you still want to use them in hydrothermal processing, roast the bran separately and sprinkle evenly on the steamed mass on the table in a clean area.

How much bran can be added? It depends on the % of nitrogen that is in the main component of the substrate – husk or straw. Start with 3% and watch the party grow. Mold will start – stop experimenting.

5. Alfalfa and other legume hay

Alfalfa hay increases the nitrogen content in the substrate.
The addition of alfalfa markedly increases yields when the substrate is made by xerothermia or tunnel pasteurization.
Grassland hay, made up of various grasses, can have between 1 and 2 N, depending on which grasses it contains.
Hay cannot be used as the main component for the substrate. Meadow hay has a too soft structure, as a result of which the substrate becomes waterlogged and rots.

How to calculate the amount of raw materials and additives for the production of oyster mushroom substrate.

Submit your raw materials for nitrogen analysis according to Kjeldahl in the agro-laboratory.
It is especially important to do such an analysis for hay.
If nitrogen in straw varies under different growing conditions from 0.25 to 0.5 (0.6 is extremely rare), then in legume hay (even of the same species!) It can be from 1.2 to 4.2.

Mix 3-4 kg of raw materials taken from different bales or bags, make an average sample and submit for analysis.

When you have the results of the analysis in your hands, the composition of the raw materials for the substrate is calculated according to the so-called cross formula:

the mass fraction of hay is equal to the value of the fraction, where the numerator is the difference between the values of substrate nitrogen and straw nitrogen; and the denominator is the difference between hay nitrogen and straw nitrogen

For example:

substrate nitrogen	0,78
hay nitrogen	3,55
straw nitrogen	0,43
mass fraction of hay	0,11

0.78-0.43/3.55-0.43 is equal to 0.11.

In other words, in order to have a substrate with a nitrogen content of 0.78 at the output, it is necessary to take 11% hay and 89% straw.

The calculation is based on dry matter, and if the components have the same moisture, you can immediately use this formula. If the moisture content of the raw materials is different, it is necessary to recalculate the number of components, taking into account the moisture content. That is, take not 11% of the hay that is actually there, but first calculate how much dry matter is contained in that particular hay and straw that you will use.

Procurement of raw materials

Straw and hay must be prepared immediately for the whole season during summer field work.

In the summer the raw materials are dry (6-10% moisture content) and, putting them in storage, you will be sure of the quality and proper storage. If you buy bales of straw and hay during the season, you must remember that at a moisture content of about 20%, the activity of microorganisms begins, the stack begins to warm up with the release of heat, and this process is not always noticeable on the surface of the bales.

Dry bean hay in bales should be stored under a shed or in a covered warehouse. Bales lying in the open air heat up and deteriorate within two to three months. This is due to the presence of protein foods readily available to bacteria and the ability to quickly draw in moisture from the surrounding air.

As a rule, straw collected from fields is distinguished by a large amount of nitrogen (0.5-0.6), where:

perennial leguminous plants have grown before;
there were black couples;
applied nitrogen and phosphorus fertilizers (especially in combination with foliar feeding)
it rained two or three weeks before the start of harvesting (in this case, organic protein compounds are partially transferred from the grain to the stem);
there are soft dry parts of young plants – weeds, which began to grow shortly before the grain harvest. At the same time, the presence of rough thick trunks of weeds does not add quality, but significantly increases the risk of straw infection with various molds. Therefore, it is better not to harvest such raw materials.

Reeds for growing oyster mushrooms

Bulrush (Scírpus) is also called cattail and reed (Phragmites australis). These are three different plants.
They are crushed and processed in the same way as straw.
But their stems are much tougher. If the heat treatment is carried out for less than 6 hours, wet spots and the development of trichoderma are very likely.

It is better not to use the soft parts of the reed with a panicle, as they are easily waterlogged.

There is no need to expect high yields from reeds, there is little nitrogen there.

I do not recommend using reeds to steam a large number of blocks. If you have a desire, you can experiment – mix with soft meadow hay and determine the yield.